Method for inspecting silicon wafer, method for manufacturing silicon wafer, method for fabricating semiconductor device, and silicon wafer

ABSTRACT

The present invention provides a method for inspecting a silicon wafer making it possible to identify and efficiently detect a new defect affecting a device fabricating process, a method for manufacturing a silicon wafer enabling manufacture of wafers not having the defect, a method for fabricating a semiconductor device using the silicon wafer not having this defect, and the silicon wafer not having the defect. When a silicon wafer is inspected, inspection is made for a defect having the entire defect size of 0.5 μm or more in which microdefects gather in a colony state.

TECHNICAL FIELD

The present invention relates to a method for inspecting a silicon wafer(hereinafter may be simply referred to as a “wafer”), and morespecifically to a method for inspecting a silicon wafer for detecting anew defect which has not been identified, a method for manufacturing asilicon wafer having no such defect, a method for fabricating asemiconductor device using the silicon wafer having no such defectabove, and the new silicon wafer having no such defect.

BACKGROUND ART

Generally a method for manufacturing a silicon wafer comprises a slicingstep of slicing a single crystal ingot to obtain a thin disk-shapedwafer; a chamfering step of chamfering a peripheral edge portion of thewafer obtained through the slicing step to prevent cracking and chippingof the wafer; a lapping step of flattening this wafer; an etching stepof removing machining deformation remaining in the so chamfered andlapped wafer; a polishing step of making a mirror surface of the wafer;and a cleaning step of cleaning the polished wafer to remove a polishingagent or dust particles deposited thereon. Only the main steps arelisted above, and sometimes other steps such as a heat treatment stepmay be added, or the step sequence may be changed. The silicon wafermanufactured as described above is finally subjected to a quality check,then is packaged in a container for accommodating wafers therein, and issent to a device fabricating company (or step).

With the manufacturing steps as described above, recently in associationwith the tendency that devices have been becoming more and more minute,demands for device performance to be achieved have become increasinglysevere, and further the silicon wafer is required to have completenessof the crystal quality and cleanliness of the wafer surface.

To satisfy the demands, it is necessary to evaluate quality of thesilicon wafer under stringent conditions, and to improve the processingfor manufacturing the silicon wafer and fabricating the device using thesilicon wafer therein.

In the silicon wafer, completeness of the crystal quality is largelyspoiled by existence of impurities, microdefects, strain fields and soon. On the silicon wafer surface, heavy metals, organic materials,particles and surface roughness also cause problems.

As a defect causing a problem in a device fabricating process, there hasbeen known a COP (Crystal Originated Particle) appearing in the vicinityof a surface layer of the wafer. The COP is generally defined as adefect with the size of 0.1 μm or less, but it appears on the wafersurface as a pit, that is, a defect with the size on the order of 0.1 to0.5 μm which can be observed by processing the wafer with anammonia-hydrogen peroxide solution (also referred to as a “SClsolution”). These are defects generated when the crystal is pulled.

A FPD (Flow Pattern Defect) having closely related to an oxide filmdielectric breakdown strength is a ripple-like defect appearing whenpreferential etching is performed with an etching liquid based onhydrofluoric acid and potassium bichromate.

There have been known other defects such as a LSTD (Laser ScatteringTomography Defect) detected by the laser scattering tomography, andthese defects are microdefects having similar behavior during growth ofthe crystal.

Further it is known that such defects as an OSF (Oxidation-inducedStaking Fault) largely affect performance of a device.

To evaluate these defects, generally preprocessing is performed to asilicon wafer itself prior to start of the evaluation, and then thedefects are directly monitored visually, with an electronic microscopeor the like.

DISCLOSURE OF THE INVENTION

It has been considered that there may exist other defects affecting thedevice fabricating step in addition to those described above. It isgenerally considered that the defects are of different types from theCOP, FPD, LSTD, and OSF, but particular features of the defects have notbeen clarified.

Therefore it has been difficult to accurately and finely evaluatequality of a silicon wafer and to improve the processes formanufacturing the silicon wafer and fabricating a device.

The present inventor has discovered a new type of defect having theentire defect size of 0.5 μm or more which is different from the crystaldefects of the silicon wafer such as a COP previously known and in whichmicrodefects gather in a colony state. This defect may especially affecta yield in the device fabricating step.

This new type of defect is described in more details below. There is nodifference between irregularities in the defect area and those in otherarea of the silicon surface. For instance, this defect can not bedetected with an AFM (Atomic Force Microscope) at all.

An atomic force microscope (AFM) monitors a surface by making use ofatomic forces working when atoms at the tip of the probe are approachedto a sample and controlling the probe for keeping the atomic forces at aconstant level. The resolution of the atomic force microscope (AFM) is0.1 nm or below.

This new type of defect can be detected by performing appropriate imageprocessing with a laser microscope based on a confocal optical system.

The confocal optical system detects quantities of light having passedthrough a pinhole by irradiating converged light beams on a fine spot ona sample and re-converging the reflected light to the pinhole fitted tothe front of a light receiver.

As shown in FIG. 7, a laser microscope 10 based on this confocal opticalsystem comprises a laser light source 14 such as an argon ion laser, alight detector 24 such as a photodiode, a beam splitter 16, a pinhole 20a and others. This laser microscope 10 is described in detail later.

This new type of defect can also be evaluated by cleaning with a SClsolution. However, this evaluation method becomes problematically adestructive inspection. Further to achieve an easy observation bycleaning with the SCl solution, the etching time is desired to belonger, but as etching proceeds, the wafer surface becomes rougher, sothat the new defect discovered in the present invention can hardly bedifferentiated from the COP.

As the newly discovered defect described above gives influence on ayield in the device fabricating step, it has been found that the waferhaving a defect evaluated and observed by the evaluation methoddescribed above should not be sent to the device fabricating step. Thepresent invention has been completed based on the finding.

It is an object of the present invention to provide a method forinspecting a silicon wafer making it possible to identify andefficiently detect a new type of defect affecting a device fabricatingstep, a method for manufacturing a silicon wafer not having the defectas described above, a method for fabricating a semiconductor deviceusing the silicon wafer not having the defect as described above, andthe silicon wafer not having the defect itself.

To solve the problems described above, a method for inspecting a siliconwafer according to the present invention comprises the step of, wheninspecting the silicon wafer, inspecting a defect having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate. In this new type of defect, several tens to several hundredsmicrodefects each having the size on the order of 0.05 to 0.5 μm gatherto form a colony-like defect. Depending on the number of gatheringmicrodefects, even the small defect is detectable as one having the sizeof at least 0.5 μm. There may be found the large defect having the sizeon the order of 3 to 10 μm.

The defect can be inspected with a laser microscope based on a confocaloptical system or a dark field microscope. There is no differencebetween irregularities in the defect area and those in other area of thewafer surface; therefore the defect can not be evaluated with an atomicforce microscope (AFM). After preprocessing is performed with anammonia-hydrogen peroxide solution (a SCl solution) and the defect areais etched, the defect may be evaluated and detected, but in this casethe inspection becomes a destructive one. Further this type of defectcan hardly be differentiated from the conventional type of defect suchas a COP. For evaluation as a non-destructive inspection, it ispreferable to perform the inspection with the laser microscope based onthe confocal optical system.

It has been found that, in addition to the laser microscope based on theconfocal optical system, also a dark field microscope can be used forthe evaluation. The dark field microscope is used for observing lightscattered by defects or particles when irradiating laser beams on asample to be monitored in the state where the entire measurement systemis placed under a dark condition, and also this dark field microscopecan be used for the evaluation as a non-destructive inspection.

A first aspect of a method for manufacturing a silicon wafer accordingto the present invention comprises the steps of: polishing the siliconwafer; cleaning and drying the polished silicon wafer; and inspecting adefect having the entire defect size of 0.5 μm or more in whichmicrodefects gather in a colony state with a laser microscope based on aconfocal optical system or a dark field microscope after the cleaningand drying step.

A second aspect of a method for manufacturing a silicon wafer accordingto the present invention comprises the steps of: mirror polishing thesilicon wafer; cleaning and drying the mirror polished silicon wafer;and preventing deposition of impurities on a surface of the wafer andalso generation of a defect having the entire defect size of 0.5 μm ormore in which microdefects gather in a colony state after the wafer ismirror polished.

A method for fabricating a semiconductor device according to the presentinvention comprises the steps of: inspecting a defect having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate in a silicon wafer; selecting the silicon wafer not having thedefect; and fabricating the semiconductor device by using the siliconwafer not having the defect.

A silicon wafer according to the present invention is the silicon waferwhich is mirror polished and has no defect having the entire defect sizeof 0.5 μm or more in which microdefects gather in a colony state.

This new type of defect to be inspected by the inspecting methodaccording to the present invention is different from any crystal defect,and is conceivably generated by contamination by impurities generated inthe polishing step and afterward such as metallic impurities, anon-uniform surface state after polishing (such as the state wherealkaline components of a polishing agent remain partially on the surfaceor hydrophilic areas and hydrophobic areas have been generated), ordeposition of silicon particles or other particles floating in the air.Generation of this type of defect can be prevented by preventingdeposition of impurities on the wafer surface after polishing.

Therefore, to manufacture a wafer not having the defect as describedabove, it is required to prevent deposition of impurities immediatelyafter the wafer is polished. For instance, storage of a just polishedwafer is conducted in water and the storage water is controlled tomanufacture the wafer by adding citric acid and a surfactant, a hydrogenperoxide solution and citric acid, or the like for preventing metals asa kind of the impurities from being deposited on a surface of the wafer.While a final wafer is manufactured, after the storage described above,through several steps including a cleaning step and a packaging step(and an inspecting step), contamination may occur by impurities from theatmosphere during the cleaning and packaging steps after the polishingstep, or from, for instance, a container for shipment used for shippingthe wafer product, so in the wafer manufacturing process carefulattentions are required for preventing the contamination as describedabove.

By paying careful attentions for preventing contamination by impuritiesafter the polishing step, a wafer not having these defects can beconstantly manufactured.

Apart from the above-described wafer manufacturing method, it is alsodesirable to include a step for inspecting a defect having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate with a laser microscope based on a confocal optical system or adark field microscope in the manufacturing process and especially toinclude the inspecting step after the polishing step but before thepackaging step.

When the inspecting step is included in the manufacturing process, awafer which may lower a yield can preferably be removed. Further thelaser microscope based on the confocal optical system or the dark fieldmicroscope enables a non-destructive inspection, so that the inspectingstep can be performed as a part of the general manufacturing process.

By selecting a wafer not having the defect having the entire defect sizeof 0.5 μm or more as described above in which microdefects gather in acolony state, it is possible to fabricate a device by using the wafer inthe device manufacture process with a high yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a micrograph showing a silicon wafer taken by a lasermicroscope based on a confocal optical system in Experimental Example 1;

FIG. 2 is a schematic view showing the silicon wafer in FIG. 1;

FIG. 3 is a micrograph showing a silicon wafer taken by an atomic forcemicroscope (AFM) in Experimental Example 1;

FIG. 4 is a schematic view showing the silicon wafer in FIG. 3;

FIG. 5 is a micrograph showing a silicon wafer taken by an atomic forcemicroscope (AFM) in Experimental Example 2;

FIG. 6 is a schematic view showing the silicon wafer in FIG. 5;

FIG. 7 is a general explanatory view showing a basic structure of thelaser microscope based on the confocal optical system;

FIG. 8 is a flow chart showing one embodiment of procedures forinspecting the wafer;

FIG. 9 is a general explanatory view showing a basic structure of a darkfield microscope;

FIG. 10 is a micrograph showing a silicon wafer taken by the dark fieldmicroscope in Experimental Example 3; and

FIG. 11 is a schematic view showing the silicon wafer in FIG. 10.

BEST MODE FOR CARRYING OUT THE INVENTION

A laser microscope based on a confocal optical system and a dark fieldmicroscope used in the method according to the present invention andprocedures for inspecting a wafer with the microscopes are describedwith reference to FIG. 7, FIG. 8, and FIG. 9, but it is to be noted thatthe present invention is not limited to the embodiments shown in thesefigures, and it is needless to say that various modifications arepossible within the scope of the technical idea of the presentinvention.

FIG. 7 is a general explanatory view showing a basic structure of alaser microscope based on a confocal optical system. In FIG. 7, thereference numeral 10 indicates a laser microscope based on a confocaloptical system, in which a laser beam source 14 such as an argon laseris provided at a position opposite to a microscope body 12.

The microscope body 12 comprises a beam splitter 16 for splitting laserbeams B from the laser beam source 14 to a plurality of laser beams B,an object lens 18 for converging the laser beams B onto a surface of awafer W to be inspected, a converging lens 22 for converging the laserbeams B reflected from a surface of the wafer W into a pinhole 20 a of apinhole member 20, and a light detector 24 for receiving the laser beamsB having passed through the pinhole 20 a.

With the configuration as described above, now the principle ofoperations thereof is described below.

1) The laser beams B from the laser beam source 14 are split by thelaser beam splitter 16 to a plurality of laser beams B.

2) All of the laser beams B are converged and irradiated by the objectlens 18 onto a surface of the wafer W with a spot of, for instance,about 0.4 μm, and concurrently are scanned in the horizontal directionkeeping a space between the laser microscope 10 and the wafer W at aconstant value.

3) The laser beams B reflected on a surface of the wafer W returnthrough the optical system, and are converged by the converging lens 22and introduced through the pinhole 20 a of the pinhole member 20 intothe light detector 24.

4) When there are defects on a surface of the wafer W, a wave front ofthe reflected light from the defect area is disturbed, and a spot of thelaser beams B expand, so that the light detecting signal isdeteriorated.

5) A defect detecting circuit not shown in the figure detects adifference between signals in the light detector 24, determines that thearea where a signal intensity difference with a signal amplitude higherthan a prescribed value is generated is a defect area, and records thesize and coordinates of the area.

6) An inspection is carried out by moving the laser beams B at aconstant speed, and each beam spot scans the entire surface of the waferW minutely.

Procedures for inspecting the wafer W with the laser microscope 10 basedon the confocal optical system described above are described below withreference to FIG. 8. FIG. 8 is a flow chart showing one embodiment ofprocedures for inspecting the wafer W.

More specifically, the wafer inspecting procedures in the waferinspecting method according to the present invention are as describedbelow.

1) A wafer is loaded on a wafer cassette and set in a loader section(step 100).

2) An order of wafers to be inspected and a recipe concerning suchfactors as sensitivity for inspection are prepared in the operatorconsole section (step 101).

3) The wafers to be inspected are automatically aligned and inspectedsuccessively (step 102).

4) A defect map and a histogram reflecting a result of inspection in theinspected area are displayed during the wafer inspection, and aninspection result file is automatically prepared (step 103).

5) An image of any defect area specified from the defect map screen canbe monitored after completion of the wafer inspection (step 104).

When an optional video printer is used together with the lasermicroscope based on the confocal optical system used in Examplesdescribed below, it is possible to print out a monitor screen. Furtherthe defect area detected as described above can also be analyzed fromdifferent points of view by converting the coordinate file formatreflecting a result of inspection to a coordinate file format for otherdevices such as a scanning electron microscope (SEM) or an atomic forcemicroscope (AFM).

FIG. 9 is a general explanatory view showing a basic structure of a darkfield microscope. In FIG. 9, the reference numeral 30 indicates a darkfield microscope, and the dark field microscope 30 has an opticalmicroscope body 32 with the measurement system set in a dark field. Alaser beam source 34 such as an argon laser is provided in relation tothe optical microscope body 32. When the laser beams B from the laserbeam source 34 are irradiated onto a surface of the wafer W, the laserbeams B are scattered due to a defect 1 and the like of the wafer W, andthe scattered laser beams S are again converged and detected by amonitoring unit (detector) 44 such as a CCD camera.

With the configuration as described above, now the principle ofoperations thereof is described below.

1) The laser beams B are irradiated from the laser beam source 34 onto asurface of the wafer W in the state where the measurement system is setin a dark field.

2) When scanning is performed on a surface of the wafer W, the laserbeams B are scattered in an area having the defect 1.

3) This scattered light (laser scattering) is converged with an opticalmicroscope and is detected with a detector 44.

EXAMPLES

The present invention will be described more specifically below by wayof following Examples which should be construed as illustrative ratherthan restrictive.

Experimental Example 1 Inspection with a Laser Microscope Based on aConfocal Optical System (Non-destructive Inspection)

A silicon wafer was monitored and inspected with the MAGICS (productname) made by LASERTEC CORP. as a laser microscope based on a confocaloptical system. The inspection carried out with the laser microscopebased on the confocal optical system is not destructive, and anyspecific preprocessing is not required.

The sample silicon wafer was manufactured by the general method. Namely,silicon single crystal ingot was sliced, and a peripheral edge portionof the sliced wafer was chamfered to prevent cracking and chippingthereof. The wafer was lapped to be flattened, etched to removemachining deformation, polished for making a mirror surface of thewafer, cleaned and dried. The cleaned and dried sample wafer wasevaluated.

A result of monitoring the defects is shown in FIG. 1 and FIG. 2. FIG. 1is a micrograph showing a surface of the sample silicon wafer taken withthe MAGICS, and FIG. 2 is a schematic view showing the silicon wafer inFIG. 1. The reference numeral 1 in FIG. 1 and FIG. 2 indicates a defect(defect 1) which may cause troubles in the device fabricating process.From the micrograph of FIG. 1 and the schematic view of FIG. 2, it isunderstood that dot-like defects gather in the colony state to form adefect area with the size of 0.5 μm or more as a whole. The defect 1shown in FIG. 1 and FIG. 2 indicates a representative defect observed ona wafer surface. The entire size of each defect varies according to thegathering state of the microdefects, but a plurality of defects 1 eachhaving the similar colony-like form and the size on the order of 0.5 μmto 10 μm were observed on the wafer surface. The size of the defect 1shown in FIG. 1 and FIG. 2 was about 6 μm.

The reference numeral 2 in FIG. 1 and FIG. 2 indicates a defect (defect2) which can be observed with an atomic force microscope (AFM). Thisdefect 2 was used as a mark so that the defect 2 could be confirmed atthe same position also in other evaluation methods. Namely, monitoringwas performed under a fixed point observation.

Then irregularities of the defect surface were evaluated with the atomicforce microscope (AFM). The SPA 360 from SEIKO INSTRUMENTS INC. was usedas the atomic force microscope (AFM).

Using the defect 2 as a mark, the defect was confirmed at the sameposition in FIG. 1 and FIG. 2. A result of monitoring with the atomicforce microscope (AFM) is shown in FIG. 3. FIG. 3 is a micrographshowing a surface of the silicon wafer taken with the SPA 360, whileFIG. 4 is a schematic view showing the silicon surface in FIG. 3. Asclearly understood from FIG. 3 and FIG. 4, the defect 1 observed in FIG.1 and FIG. 2 could not be detected even when irregularities of the wafersurface were monitored with the atomic force microscope (AFM), and it isconsidered that this defect has no irregularities and that this defectis caused by impurities gathering in a strained portion within the wafer(an uppermost surface layer).

Experimental Example 2 Inspection After Long Time Processing with a SClSolution (Destructive Inspection)

The silicon wafer observed in Experimental Example 1 was processed witha SCl solution (a chemical solution with the volumetric ratio of 28 wt %ammonia water: 30 wt % hydrogen peroxide solution: water=10:2:100) for40 minutes under the solution temperature of 80° C. The wafer immersedin the solution was then monitored and inspected with an atomic forcemicroscope (AFM).

A result of observation of the defect is shown in FIG. 5 and FIG. 6.FIG. 5 is a micrograph showing a surface of the silicon wafer taken withthe SPA 360, while FIG. 6 is a schematic view showing the surface ofsilicon wafer shown in FIG. 5. The area of defect 1 not observed withthe atomic force microscope (AFM) (see FIG. 3 and FIG. 4) was etchedwith a chemical solution with the SCl composition, and the defect 1could be observed as shown in FIG. 5 and FIG. 6.

As described above, this new defect 1 is different from a defect causeddue to the crystalline structure such as a COP, and it can be consideredthat this defect is caused due to any defect in an uppermost surfacelayer of the wafer surface, especially strain therein.

Experimental Example 3 Inspection with a Dark Field Microscope

A silicon wafer was observed with the SPA 360 from SEIKO INSTRUMENTSINC. as a dark field microscope. This SPA 360 is a unit provided withdifferent two types of microscopes, namely the atomic force microscope(AFM) and the dark field microscope, and this unit enables observationwith a dark field microscope at the same position where measurement isperformed with the AFM.

The sample silicon wafer was a wafer with a defect having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate (the wafer used in Experimental Example 1), and the defect wasconfirmed with a laser microscope based on the confocal optical system.

A result of observation of the defect is shown in FIG. 10 and FIG. 11.FIG. 10 is a micrograph showing the silicon wafer taken with a darkfield microscope, while FIG. 11 is a schematic view showing the siliconwafer shown in FIG. 10. Observation was performed at about ×50magnification. Although the microdefects can not be differentiated fromeach other, these figures show that the defect having the same form asthat of the defect 1 observed with the laser microscope based on theconfocal optical system can be observed. A defect having the ordinaryirregularities (such as the defect 2 observed as a mark) or a particlecan be detected with the dark field microscope because scattering of thelaser beams occurs, but it was found that also the defect having noirregularities found in the present invention could be observed with thedark field microscope. It can be considered that this new type of defectcan be observed with the dark field microscope because this defect is aspecific one. Namely, although this defect has no irregularities, it canbe considered that the defect reflects a difference in surface qualitybetween the defect area and other normal area in the vicinity thereof,especially a difference in density due to impurities present on thewafer surface.

Example 1

A sample silicon wafer subjected up to the polishing step by followingthe same sequence as that in Experimental Example 1 was prepared, andthe polished sample wafer was stored in a pit tank containing citricacid and hydrogen peroxide solution to prevent impurities such as metalcontamination as much as possible, and then was subjected to thecleaning step. Contamination by heavy metals was prevented also duringthis cleaning step, and then the sample was dried. Even after the stepsdescribed above, the sample was kept under an environment where thequantities of particles in the atmospheric air were 1000 pieces percubic feet or less, and the sample wafer was monitored and evaluatedwith a laser microscope based on a confocal optical system immediatelyafter the sample was taken out from the environment. The defect 1 havingthe entire defect size of 0.5 μm or more in which microdefects gather ina colony state as shown in FIG. 1 was not observed.

Comparative Example 1

A sample silicon wafer subjected up to the polishing step by followingthe same sequence as that in Experimental Example 1 was prepared, andthe polished sample wafer was stored in pure water, took out from thewater and left intentionally under the atmospheric air for a while, andthen was cleaned. In these steps, the sample wafer was intentionallycontacted to unspecified impurities. Then the sample silicon wafer wasmonitored and evaluated with a laser microscope based on a confocaloptical system. A plurality of defects 1 having the entire defect sizeof 0.5 μm or more in which microdefects gather in a colony state asshown in FIG. 1 and FIG. 2 were observed. In the wafers (8-inch wafer)observed as described above, 10 to 30 colony-like defects each havingthe size on the order of 1 to 5 μm were present on a surface of thewafer, especially in the peripheral area thereof.

Manufacturing Example 1

The wafer manufacturing process described hereinafter comprises a stepfor inspecting a defect having the entire defect size of 0.5 μm or morein which microdefects gather in a colony state with a laser microscopebased on a confocal optical system, and the inspecting step was locatedbetween a cleaning and drying step and a packaging step.

Steps up to the cleaning and drying step in the wafer manufacturingprocess were carried out in a plurality of lines to evaluate wafers. Theabove-described defect was observed in some lines, but was not observedin other lines. In the manufacturing process wherein the defect wasobserved, the water used for storing a polished wafer was only purewater. When hydrogen peroxide solution and citric acid were added to thewater for storing wafers therein, the defect was not observed in thewafer manufactured in the line. As described above, the manufacturingprocess can be improved by the use of the result obtained in theinspection step with the laser microscope based on the confocal opticalsystem.

When the wafer recognized as having a defect, especially a wafer havingthe relatively larger defect with the size of 0.5 μm or more was used inthe device fabricating process, the yield became lower. In theinspecting step, the defect was recognized visually or by the imageprocessing, and wafers not having the defect were selected and used inthe device fabricating process, so that the yield was improved.

From the results of various experiments described above, a new defectaffecting the yield in the device fabricating process was found. It wasalso confirmed that the wafer not having the defect as described aboveshowed the excellent performance. Further it was found that the defectcould easily be found with a laser microscope based on a confocaloptical system. Therefore by selecting only wafers not having the defectand sending the selected wafers to the device fabricating process, theyield can be improved. It was also found that it was required to preventand control contamination by impurities after polishing for protectionagainst this type of defect. Also it was found that the defect could bedetected, in addition to the laser microscope based on the confocaloptical system, also with a dark field microscope, and that, in thatcase, the same effect as that obtained by the laser microscope could beobtained. It is preferable to use a microscope capable of sensing achange in a quantity of detected light (difference in contrast).

It is to be noted that the present invention is not limited to theembodiments described above. For instance, the defect which can beobserved with the laser microscope based on the confocal optical systemor the like, namely the defect without irregularities having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate is often observed after the polishing step. It can be consideredthat, as a surface of a polished wafer is in an active state, thesurface is easily affected when the surface is contacted to impuritieswhich are considered to be a cause for the defect. The active state ofthe wafer surface is also generated after epitaxial growth or on asurface of a wafer processed by, for instance, a hydrofluoric acidsolution, with the result that similar defects may be observed.Inspection of wafers after epitaxial growth or wafers processed byhydrofluoric acid and selection of wafers having no defect after thesesteps are also included in a technical scope of the present invention.

Capability of Exploitation in Industry

As described above, with the method for inspecting a silicon waferaccording to the present invention, it is possible to efficiently detectand identify a new defect of a silicon wafer which may affect a devicefabricating process (a defect having the entire defect size of 0.5 μm ormore in which microdefects gather in a colony state). With the methodfor manufacturing a silicon wafer according to the present invention, awafer not having this new type of defect can be manufactured. Furtherwith the method for fabricating a device according to the presentinvention, the yield in the device fabricating process can be improvedby using a silicon wafer not having this new type of defect. The siliconwafer according to the present invention does not have this new type ofdefect, and can contribute to improvement of yield in the devicefabricating process.

1. A method for inspecting a silicon wafer comprising the step of, wheninspecting the silicon wafer, inspecting a defect having the entiredefect size of 0.5 μm or more in which microdefects gather in a colonystate.
 2. A method for inspecting a silicon wafer according to claim 1,wherein the defect is inspected with a laser microscope based on aconfocal optical system or a dark field microscope.
 3. A method formanufacturing a silicon wafer comprising the steps of: polishing thesilicon wafer; cleaning and drying the polished silicon wafer; andinspecting a defect having the entire defect size of 0.5 μm or more inwhich microdefects gather in a colony state with a laser microscopebased on a confocal optical system or a dark field microscope after thecleaning and drying step.
 4. A method for manufacturing a silicon wafercomprising the steps of: mirror polishing the silicon wafer; cleaningand drying the mirror polished silicon wafer; and preventing depositionof impurities on a surface of the wafer and also generation of a defecthaving the entire defect size of 0.5 μm or more in which microdefectsgather in a colony state after the wafer is mirror polished.
 5. A methodof fabricating a semiconductor device comprising the steps of:inspecting a defect having the entire defect size of 0.5 μm or more inwhich microdefects gather in a colony state in a silicon wafer;selecting the silicon wafer not having the defect; and fabricating thesemiconductor device by using the silicon wafer not having the defect.6. A silicon wafer which is mirror polished and has no defect having theentire defect size of 0.5 μm or more in which microdefects gather in acolony state.